A cellular mobile communication wireless access system and a wireless network (hereinafter, referred to as “Long Term Evolution (LTE)” or “Evolved Universal Terrestrial Radio Access (EUTRA)”) have been examined in the 3rd Generation Partnership Project (3GPP). In the LTE system, a base station device is also referred to as evolved NodeB (eNodeB) and a terminal device is also referred to as user equipment (UE). The LTE system is a cellular communication system in which a plurality of coverage areas of the base station device are arranged in a cell shape. A single base station device may manage a plurality of cells.
The LTE system corresponds to a time division duplex (TDD) system. The LTE system using the TDD system is also referred to as a TD-LTE system or an LTE TDD system. The TDD system is a technique that performs time division multiplexing on an uplink signal and a downlink signal in order to perform full duplex communication in a single frequency band.
In the 3GPP, application of interference management and traffic adaptation (IMTA) to the TD-LTE system has been examined. Traffic adaptation is a technique that changes the ratio of uplink resources to downlink resources depending on uplink traffic and downlink traffic.
NPL 1 discloses a method of using a flexible subframe as a method for achieving traffic adaptation. The base station device can receive uplink signals or transmit downlink signals in the flexible subframe. In NPL 1, the terminal device regards the flexible subframe as a downlink subframe as long as the base station device does not instruct the terminal device to transmit the uplink signals in the flexible subframe. The traffic adaptation technique is also referred to as dynamic TDD.
NPL 1 discloses a technique that determines hybrid automatic repeat request (HARQ) timing for a physical downlink shared channel (PDSCH) on the basis of the uplink-downlink configuration to be newly introduced and determines the HARQ timing for a physical uplink shared channel (PUSCH) on the basis of the initial UL-DL configuration.
NPL 2 discloses the following techniques: (a) a UL/DL reference configuration which is introduced; and (b) some subframes which are scheduled for uplink or downlink by a dynamic grant/assignment from a scheduler.
A procedure of the terminal device for reporting channel state information (CSI) is described in section 7.2 of NPL 3. The base station device allocates downlink resources to the terminal device on the basis of the channel state information reported from a plurality of terminal devices. The channel state information includes a channel quality indicator (CQI).